On Fri, 24 Mar 2017 13:12:54 -0500 Josh Poimboeuf <jpoim...@redhat.com> wrote:
> Instead I was able to "fix" it by ignoring ftrace calls in real mode: > > ----- > index 8f3d9cf..5c0d0c6 100644 > --- a/arch/x86/kernel/ftrace.c > +++ b/arch/x86/kernel/ftrace.c > @@ -983,6 +983,9 @@ void prepare_ftrace_return(unsigned long self_addr, > unsigned long *parent, > unsigned long return_hooker = (unsigned long) > &return_to_handler; > > + if (__builtin_return_address(0) < TASK_SIZE_MAX) > + return; > + > if (unlikely(ftrace_graph_is_dead())) > return; > --------------- > > I'm not sure what the best fix should really be. A few ideas off the > top of my head: > > - A real mode check similar to the above (except it should probably be > more precise) The real mode check hack may be good enough for now. Make sure that it's commented well. -- Steve > > - Make tracing_graph_pause a percpu variable so that it can be read from > prepare_ftrace_return() > > - pause_graph_tracing() from ftrace_suspend_notifier_call() > > Steven, thoughts? >
